In a digital decimation filter, a target frequency response is characterized by a flat pass-band region, which is in a frequency range where a signal of interest is located, and a stop-band region, which has a large attenuation in a frequency range where noise, aliases and interferers are present. A transition between the pass-band region and the stop-band region is ideally as sharp as possible.
A decimation filter may be used to observe whether a sensor output signal, which changes quickly between levels as in a step response, is above a critical threshold indicating an error condition. As can be seen in FIG. 2B, the step response has a large overshoot indicated by reference numeral 230, which could result in a false alarm. The overshoot is 8% higher than the true, final level, requiring that the threshold be set at least 10% higher than actually required.